The antineoplastic agent, cytarabine, is a most successful agent for treatment of leukemia. It has been reported that one of the side effects is a neuropathy relating to the cerebellum. this has been shown using standard neuropathological techniques, i.e., sectioning and cellular staining, to result in destruction of a specific cerebellar cell type, the Purkinje cell. Considering the size of these cells in the rat, 30_40 fm, it is of interest to determine whether MR microscopy can be used to identify this change in cellular organization in the intact cerebellum.